title: Direct monitoring of the strand passage reaction of DNA topoisomerase II triggers checkpoint activation.
abstract: By necessity, the ancient activity of type II topoisomerases co-evolved with the double-helical structure of DNA, at least in organisms with circular genomes. In humans, the strand passage reaction of DNA topoisomerase II (Topo II) is the target of several major classes of cancer drugs which both poison Topo II and activate cell cycle checkpoint controls. It is important to know the cellular effects of molecules that target Topo II, but the mechanisms of checkpoint activation that respond to Topo II dysfunction are not well understood. Here, we provide evidence that a checkpoint mechanism monitors the strand passage reaction of Topo II. In contrast, cells do not become checkpoint arrested in the presence of the aberrant DNA topologies, such as hyper-catenation, that arise in the absence of Topo II activity. An overall reduction in Topo II activity (i.e. slow strand passage cycles) does not activate the checkpoint, but specific defects in the T-segment transit step of the strand passage reaction do induce a cell cycle delay. Furthermore, the cell cycle delay depends on the divergent and catalytically inert C-terminal region of Topo II, indicating that transmission of a checkpoint signal may occur via the C-terminus. Other, well characterized, mitotic checkpoints detect DNA lesions or monitor unattached kinetochores; these defects arise via failures in a variety of cell processes. In contrast, we have described the first example of a distinct category of checkpoint mechanism that monitors the catalytic cycle of a single specific enzyme in order to determine when chromosome segregation can proceed faithfully.
authors.affiliation: Department of Genetics, Cell Biology & Development, University of Minnesota, Minneapolis, Minnesota, United States of America.
authors.forename: Katherine L
authors.initials: KL
authors.lastname: Furniss
authors.forename: Hung-Ji
authors.initials: HJ
authors.lastname: Tsai
authors.forename: Jo Ann W
authors.initials: JA
authors.lastname: Byl
authors.forename: Andrew B
authors.initials: AB
authors.lastname: Lane
authors.forename: Amit C
authors.initials: AC
authors.lastname: Vas
authors.forename: Wei-Shan
authors.initials: WS
authors.lastname: Hsu
authors.forename: Neil
authors.initials: N
authors.lastname: Osheroff
authors.forename: Duncan J
authors.initials: DJ
authors.lastname: Clarke
mesh_terms: D002453:Cell Cycle / Q000235:genetics*; D059447:Cell Cycle Checkpoints / Q000235:genetics*; D018797:Cell Cycle Proteins / Q000235:genetics / Q000378:metabolism; D064447:Checkpoint Kinase 2 / Q000235:genetics / Q000378:metabolism; D020090:Chromosome Segregation / Q000235:genetics; D004247:DNA / Q000235:genetics*; D004250:DNA Topoisomerases, Type II / Q000235:genetics*; D006801:Humans; D018386:Kinetochores / Q000378:metabolism; D064246:Mad2 Proteins / Q000235:genetics; D012441:Saccharomyces cerevisiae / Q000235:genetics; D029701:Saccharomyces cerevisiae Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D018797:Cell Cycle Proteins; C577695:MAD2 protein, S cerevisiae; D064246:Mad2 Proteins; D029701:Saccharomyces cerevisiae Proteins; D004247:DNA; D064447:Checkpoint Kinase 2; C067022:RAD53 protein, S cerevisiae; D004250:DNA Topoisomerases, Type II